The prior art includes conventional foam rubber arch supports which may be purchased in drugstores or the like. These provide relatively little effective arch support, but have the advantage of being adaptable to nearly any foot within a given size range. Thus, they can be produced and sold inexpensively, and are readily available to the public at large.
The prior art also includes custom fitted orthotic inserts formed of incompressible materials. These are very rigid, and provide a high degree of effective arch support, but because of their rigidity, must be custom fitted to the user's foot. These devices, while very effective, are quite expensive.
A proper arch support ("orthosis") prevents excessive pronation of the foot at both heel strike and mid-stance, and at points between. Excessive pronation can occur in a weak foot during normal walking or standing; however, even a relatively strong foot will undergo excess pronation during vigorous exercise and particularly in sports like running and skiing where the legs and feet are called upon to absorb a substantial amount of shock.
Excessive pronation causes the tibia and fibula to rotate inwardly, placing strain on the leg muscles, on the medial (inner) side of the knee, and in the plantar fascia. Over time, these strains lead to injury.
Because of the cost and time involved, or for lack of information, many persons who could benefit from effective orthosis, as a preventative, neglect to seek it until after an injury has occurred. Thus, it is desirable, as a preventative measure, to make effective orthosis available conveniently and inexpensively.